Mobile communications networks are being used to support the Internet. Mobile Internet terminals (mobile nodes) require support as they move within the wireless network. The present invention efficiently solves the problem of mobile Internet connectivity while preserving bandwidth.
Mobile communications networks, commonly designated as cellular networks, are rapidly expanding to support more services beyond voice service. One of the new services is the running of Internet Protocols (IP) to support mobile access to the Internet. When mobile users access the Internet and are moving geographically the connection must be handed over between connection nodes to maintain the connection to the Internet. Handovers result from a range limitation due to the geographic limitation of communication distances between nodes within a mobile communication network.
Handovers are likely to occur while the terminal is moving within a wireless network with several access points. Simultaneous bindings are used to ensure that handovers are as smooth as possible. Using this type of binding, data packets are simultaneously routed through several access points within the geographical area surrounding the user""s last access point called a mobile node.
The problem with this solution is that excess bandwidth is used because the same data packet is sent through many access points to the terminal. The excess data packets are simply discarded at the terminal resulting in wasted transmission capacity. It is more efficient to send data packets only once to a mobile terminal.
Current Solutions to IP Mobility:
One system for providing mobility to the Internet is described in a paper published in IEEE May 1997 issue at pages 84-99, by Charles E. Perkins, of Sun Microsystems. In addition, an Internet document specifies protocol enhancements that allow transparent routing of IP datagrams to mobile nodes in the Internet and can be found at http://sunsite.auc.dk/RFC/rfc/ rfc2002.html (incorporated herein by reference in its entirety). In his May 1997 article, Mr. Perkins describes Agent Advertisement, Registration, and Tunneling as methods to support mobile IP. He further describes route optimization techniques. The following is an excerpt from Mr. Perkins paper describing the protocol, found at page 86.
xe2x80x9cMobile IP is a way of performing three related functions:
Agent Discoveryxe2x80x94Mobility Agents advertise their availability on each link for which they provide service.
Registrationxe2x80x94When the mobile node is away from home, it registers care-of-address with its home agent.xe2x80x9d
Tunnelingxe2x80x94In order for datagrams to be delivered to the mobile node when it is away from home, the home agent has to tunnel the datagrams to the care-of-address.
xe2x80x9cThe following will give a rough outline of operation of the mobile IP protocol, making use of the above-mentioned operations. FIG. 1 (not shown) may be used to help envision the roles played by the entities.
Mobility agents make themselves known by sending agent advertising messages. An impatient mobile node may optionally solicit an agent advertisement message.
After receiving an agent advertisement, a mobile node determines whether it is on its home or a foreign network. A mobile node basically works like any other node when it is at home.
When a mobile node moves away from its home network, it obtains a care-of-address on the foreign network for instance, by soliciting or listening for agent advertisement, or contacting Dynamic Host Configuration Protocol (DHCP) or Point-to-Point (PPP).
While away from home, the mobile node registers each new care-of-address with its home agent, possibly by way of a foreign agent.
Datagrams sent to the mobile node""s home address are intercepted by its home agent, tunneled by its home agent to the care-of-addresses, received at the tunnel endpoint (at either a foreign agent or the mobile node itself), and finally delivered to the mobile node.
In the reverse direction, datagrams sent by the mobile node are generally delivered to their destination using standard IP routing mechanisms, not necessarily passing through the home agent (but see the eighth section).xe2x80x9d
xe2x80x9cWhen the home agent tunnels a datagram to the care-of-address, the inner IP header destination (i.e., the mobile node""s home address) is effectively shielded from the intervening routers between its home network and its current location. At the care-of-address, the original datagram exits from the tunnel and is delivered to the mobile node.xe2x80x9d
xe2x80x9cIt is the job of every home agent to attract and intercept datagrams that are destined to the home address of any of its registered mobile nodes. The home agent basically does this by using a minor variation on Address Resolution Protocol (ARP), and to do so in the natural mode it has to have a network interface on the link indicated by the mobile node""s home address. However, the latter requirement is part of the mobile IP specification. When foreign agents are in use, similarly, the natural mode of operation suggests that the mobile node be able to establish a link to its foreign agent. Other configurations are possible, however, using protocol operations not defined by (and invisible to) mobile IP. Notice that, if the home agent is the only router advertising reachability to the home network, but there is no physical link instantiating the home network, then all datagrams transmitted to mobile nodes addressed on that home network will naturally reach the home agent without any special link operations.xe2x80x9d
xe2x80x9cFIG. 1 (not shown) illustrates the routing of datagrams to and from a mobile node away from home, once the mobile node has registered with its home agent. The mobile node is presumed to be using a care-of-address provided by the foreign agent:
A datagram to the mobile node arrives on the home network via standard IP routing.
The datagram is intercepted by the home agent and is tunneled to the care-of-address, as depicted by the arrow going through the tube.
The datagram is de-tunneled and delivered to the mobile node.
For datagrams sent by the mobile node, standard IP routing delivers each to its destination. In the FIG. (1) sic, the foreign agent is the mobile node""s default router.xe2x80x99
Further background on mobile IP can be found in another paper by Mr. Charles Perkins, Sun Microsystems and David B. Johnson, Carnegie Mellon University prepared for by the Mobile IP Working Group of the Internet Engineering Task Force (IETF), dated Feb. 25, 1999. Online reference: http://search.ietf.org/internet-drafts/. In their paper they describe a system for route optimization in Mobile IP. The system described allows for routing to a mobile node without going to the home agent first to reduce traffic and optimize routing.
Messrs. Johnson and Perkins published another IETF paper on Jun. 25, 1999 setting forth a mobility support protocol IPv6. In it each mobile node is always identified by its home address, regardless of its current point of attachment to the Internet. When a terminal is operating away from home it accesses the Internet via a care-of-address to give the current location. It allows IPv6 nodes to cache the binding of a mobiles node""s home address to its care-of-address to send the mobile packets directly to the latter. This protocol envisions searching for neighboring nodes to handover connections but does not solve the problem of duplicate data packets being sent by several nodes to a moving user. The above reference papers describe systems that support mobile IP and the invention disclosed herein. These papers are incorporated herein by reference.
Currently, mobile nodes are serviced using a simultaneous binding. In a simultaneous binding a mobile node has many care-of- addresses. When there is more than one care-of address active for a mobile node, the home agent is instructed to send a duplicated encapsulated datagram to each care-of address for forwarding by multiple foreign agents to the same mobile node.
An object of the Invention is to provide binding techniques between nodes in a mobile communications network for efficient data transmission to mobile users.
Another object of the invention is to save bandwidth when delivering data packets to mobile users of a mobile network.
Yet another object is to enable efficient access to the Internet by mobile users.
This invention is a novel binding technique for mobile Internet Protocol (IP). The present use of simultaneous bindings waste bandwidth because all foreign agents forward data packets of a data message to a mobile node. The excess packets are discarded wasting bandwidth. In contrast, the new Anycast binding registers itself in several IP sub-networks simultaneously as before but only one of the foreign agents delivers certain data packets to the mobile node. Because only one foreign agent is selected to deliver the data packets of a data message rather then many, bandwidth is saved.